PITTSBURGH (KDKA/AP) – First Amendment advocates are suing President Donald Trump, saying some of his critics have been unconstitutionally blocked from following him on Twitter.

The lawsuit was filed Tuesday in Manhattan federal court by the Knight First Amendment Institute at Columbia University.

The lawsuit says Twitter has become an important public forum for the president and he frequently makes public announcements on his @realdonaldtrump account.

The lawsuit asked a judge to stop Trump and his media team from blocking critics from following his personal account.

A Bethel Park man has joined that lawsuit after being blocked by the president.

“I sent him an innocuous tweet to start with, and on the second one called him a fake leader,” Joe Papp said.

Papp says he sent the tweet because he was upset by the decision on the Paris Accords and using Pittsburgh’s name.

The following morning, no presidential tweets.

“I tried to look at his Twitter page and got the big fat notice saying you’re not authorized to view these tweets,” Papp said.

Papp says being blocked by the president is reprehensible.

“I absolutely let people know what I thought in that our president is mentally weak and intolerant of criticism,” he says.

It’s been a month and Papp still can’t believe it.

“Can you imagine if the President of the United States is wasting his time and upset at what a guy in Bethel Park is saying,” Papp said.

The Knight First Amendment Institute at Columbia University filed the suit on behalf of Papp and six-others who have been blocked.

“It’s about respecting the Constitution and respecting the First Amendment which is something this president unfortunately is fundamentally incapable or willing to do,” Papp says.

A spokeswoman for government lawyers declined to comment.

The lawsuit says blocking people from following Trump’s account was a viewpoint-based restriction that the Constitution doesn’t permit.

The director of the Knight First Amendment Institute is Jameel Jaffer, who worked for years with the American Civil Liberties Union.

(TM and © Copyright 2017 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2017 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)

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